These giant 'drop bears' with opposable thumbs once scaled trees in Australia. But how did they grow so huge?

Peter Schouten, Author provided

Although long dead, fossil skeletons provide an incredible window into the lifestyle and environment of an extinct animal.

By analysing the various features of fossil bones we can reveal not only the overall size and shape of the animal, but also what kind of movement the animal was capable of, its lifestyle, and the environment in which it lived.